2 Answers
2

It's actually a bonus payout for the time you've been waiting in the matchmaking queue. Before, they just awarded completed games (and completed games in a row). As such, the most bonus was awarded for having lots of short games and this bonus stacked. This has been changed.

The new bonus now only pays you a bit for the time "wasted" while waiting for a game. Considering full servers you usually just wait a few seconds, but there have been times (at least in Europe) where it was possible that you've waited for 5 minutes or a bit more. Having some long waiting times in combination with payouts based on game length, people would have just tried delaying games so they get more IP out of their time (rather than waiting for another game).

The Matchmaking Bonus is meant to pay out approximately the same amount of IP for x minutes in the queue as x minutes in the game. So the ultimate goal is to have two games of 20 minutes and 5 minutes queue in between paying out the same as a 45 minutes game (making it pointless to try to win fast or late).

Sorry, no. I remember there being several FAQs and news articles back in that time, but LoL seems to be too popular to find any specific article using these rather common terms. I haven't tried using the "red tracker", but it might still be rather tedious.
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MarioNov 9 '12 at 0:13

Matched Game IP is from using Riot's Match Making system. Anything but custom games will get you this.

I believe the intent was to award IP based on the length of the game, as there used to be an incentive to surrender at 25 (and thus play multiple short games) to eke out more IP than by playing fewer, longer games.

Since that dominion game only lasted 11 minutes, the bonus is rather small.